A drone attack which brought travel chaos to thousands of passengers at Gatwick Airport was reportedly an "inside job".

A disgruntled employee is suspected to be the person responsible for flying the drone, which saw 1,000 flights cancelled and affected an estimated 140,000 passengers.

Police believe either a current or former employee was behind the December 19 incident, The Times reported.

Sussex Police were criticised for their handling of the drone attack, after wrongly arresting a couple and later suggesting there may not have been a drone at all.

Read more: Letters - Gatwick and the silver lining

The investigation has led officers to believe the attack must have been carried out by someone who would understand the layout of the airport.

The Whitehall source also claimed the drone could have “hidden” behind structures and buildings.

“[The drone pilot] knew the blind spots for it, where it could not be ‘hit’. It was clearly someone with really good knowledge of Gatwick, someone who had worked there,” the source said.

“Hypothetically it could have been a disgruntled employee.”

Gatwick Airport Limited had previously offered a £50,000 reward through Crimestoppers, for information leading to the arrest and conviction of those responsible for the incident.

A spokeswoman for Sussex Police said: “We are keeping an open mind about who is responsible and their motives.”